The tribological behaviors of graphite, non-graphitic carbon, carbon-carbon composite, and unhydrogenated amorphous carbon in nitrogen and air are investigated. The friction and wear of all carbon materials can be similarly influenced by water vapor and oxygen. Carbon materials generally exhibit a high friction and wear behavior when there is a lack of lubricant vapors in the environment. Water vapor, even in small quantities, is effective in lubricating carbon materials-a concentration of 100 ppm in nitrogen can lubricate most of the materials examined in this study. Depending on the water vapor content in the environment and the friction regime involved, oxygen can act either as a lubricant or an agent for tribochemical wear. The tribological properties of carbon materials depend on gases and vapors in the environment that can interact with carbon atoms. In spite of having a wide range of physical properties, the family of sp 2 carbon materials can exhibit similar friction and wear behaviors in various environments owing to their common valence structure.